Service apparatus for automotive air conditioning systems and like refrigeration equipment heretofore proposed in the art typically include a vacuum pump, a source of lubricant under pressure and a source of refrigerant under pressure, all adapted for selective connection to the equipment under service. In automated service apparatus, the service apparatus is first connected to refrigeration equipment to be charged, and then vacuum time, and oil and refrigerant quantities are set by the operator. The latter are typically accomplished by manipulation of calibrated dials on the apparatus operator panel. Vacuum time depends upon the capacity of the refrigeration equipment under service and the efficiency of the apparatus vacuum pump. For automotive air conditioning system, vacuum time may be on the order of twenty to thirty minutes. Oil and refrigerant charges also depends on system capacity and are specified by the manufacturer. One to ten ounces of oil and two and three-quarters pounds of refrigerant are typical for automotive systems.
When an automatic mode of operation is initiated, the vacuum pump is first operated for the time set to evacuate the refrigeration system under service. The pressurized oil source is then connected to the system for feeding thereto the quantity of oil set by the operator, and the pressurized refrigerant source is then connected to the system for feeding thereto the quantity of refrigerant set by the operator. Typically, the operator is not advised of progress during the successive stages of operation and, in the event of malfunction, is not apprised of the source of such malfunction. Furthermore, in the event of such malfunction or depletion of the oil or refrigerant supplies during a charge cycle, it is typically necessary to rebegin the entire process. Another problem in many prior art devices is difficulty of simply adding an incremental refrigerant charge when equipment under service simply has low refrigerant pressure but does not require a complete recharge. Thus, prior art apparatus are generally characterized by an absence of versatility and by difficulty of operation in use.
A general object of the present invention is to provide apparatus for servicing refrigeration equipment in which the charge variables--i.e. vacuum time, and oil and refrigerant quantities--may be readily programmed by the operator; which implements an automatic mode of operation wherein operating sequence and status is continually indicated to the operator at each stage of operation; which, in the event of malfunction, not only interrupts operation at the stage in which malfunction occurred, but also provides to the operator an error code indicative of the malfunction which occurred; which may either resume operation at the point at which malfunction occurred or rebegin the entire cycle, depending upon the nature of the malfunction; which includes facility for a manual mode of operation for testing apparatus operation; and which includes a multiplicity of self-test and diagnostic features.
A further object of the invention is to provide refrigeration equipment service apparatus of the described character which is economical to manufacture, and which may be easily used by unskilled or semi-skilled operators.
Yet another object of the invention is to provide apparatus of the described character in which a predetermined or preset quantity of refrigerant may be added to refrigeration equipment attached thereto independently of the automatic mode of operation and without requiring that the equipment be completely recharged.